1. Field of the Invention
The present invention relates to an antenna system, and more particularly, to an active smart antenna system and a fabrication method thereof.
2. Description of the Related Art
Generally, a smart antenna system is a core component necessary in a next generation communication system, and is used at a high frequency band such as a mobile vehicle satellite broadcasting/communication, a military communication, and etc. The smart antenna system can be positioned at a base station or a mobile terminal according to an arrangement size of an antenna. The smart antenna system can accommodate a large number of users, and thereby a capacity of the system can be increased.
The most core component of the smart antenna system is a phase shifter. The phase shifter can precisely pursue a usage frequency by controlling a signal. Also, the phase shifter delays a phase of an input signal by controlling a switch connected to an inductor, a capacitor, and etc. constituting the phase shifter, and thereby can convert the signal into a signal having a desired phase in an output terminal. A phase shifting apparatus that is nowadays the most applied to a vehicle satellite receiver is a passive smart antenna system for delaying a phase using a mechanical motor.
However, since the passive smart antenna system has a large size and an expensive fabrication cost, a spread ratio thereof is not high. According to this, a development of an active smart antenna system having a relatively small size and a cheap fabrication cost is absolutely required. A construction of the active smart antenna system will be explained with reference to FIG. 1.
FIG. 1 is a block diagram showing a construction of a general active smart antenna system.
As shown, the active smart antenna system comprises: an antenna 100 for transmitting and receiving a signal; a low noise amplifier (LNA) 200 for amplifying a signal received through the antenna so as to minimize a noise generation; and a phase shifter 300 for controlling a phase of the amplified signal.
Among the components constituting the active smart antenna system, the phase shifter 300 occupies a space the most and requires the most expensive cost. The phase shifter 300 is largely divided into a one-bit (constructed as 11.25° phase variator), a two-bit (constructed as 11.25° and 22.5° phase variator), a three-bit (constructed as 11.25°, 22.5°, and 45° phase variator), a four-bit (constructed as 11.25°, 22.5°, 45°, and 90° phase variator), and a five-bit (constructed as 11.25°, 22.5°, 45°, 90°, and 180° phase variator). In order to implement the active smart antenna system that can be used at a satellite broadcasting receiver, approximately one hundred of said five-bit phase shifters are necessary.
Recently, accordingly as a microwave monolithic integrated circuit (MMIC) technology is developed, a phase shifter using an electron switching device such as a high electron mobility transistor (HEMT) and a field effect transistor (FET) has been developed and an active smart antenna system using the phase shifter is actively being developed. That is, an electron switch, an inductor, a capacitor, and etc. are formed on one silicon substrate (for example, GaAs substrate), and then are packaged thus to fabricate the phase shifter 300. A technique for designing an active smart antenna system using the fabricated phase shifter 300 is being proposed.
However, in the active smart antenna system, the phase shifter 300 is constructed by combining a plurality of devices on said one silicon substrate by the MMIC technology, a semiconductor process. According to this, a fabrication cost is increased and a quality factor of the inductor (for example 8˜13) is low thus not to be able to anticipate a high quality.
Also, in the active smart antenna system, not only the phase shifter 300 but also the antenna 100, the LNA 200, or transmission/reception module have to be provided together. The components are additionally mounted on a printed circuit board (PCB) thus to be assembled. Therefore, in the active smart antenna system, a lead for bonding the fabricated phase shifter 300 on the PCB is required, thereby increasing an entire size and deteriorating a quality factor of the inductor.
According to this, an active smart antenna system capable of reducing a fabrication cost, having an inductor of a high quality factor applied thereto, and easily packaging the phase shifter 300, the antenna 100, and the LNA 200, and a fabrication method thereof are required.
As aforementioned, according to the active smart antenna system in accordance with the related art, the phase shifter is fabricated by the MMIC technology, a semiconductor process, thereby increasing a fabrication cost.
Also, according to the active smart antenna system in accordance with the related art, the phase shifter is fabricated by the MMIC technology, a semiconductor process, thereby lowering a quality thereof.
Also, according to the active smart antenna system in accordance with the related art, the phase shifter is fabricated by the MMIC technology, a semiconductor process, thereby increasing a size thereof due to an individual packaging for combining the antenna, the LNA, or the transmission/reception module.